DDA can be taken too far, I am all for equal opportunities for all, not putting keypads at dda height could be discriminating disabled users. However, putting the bell box at ladder height could also be seen as discriminating to disabled DIYers. Having a keypad at all could be described as discriminating to the mentally disabled
The keypad can be moved if a disabled person moves into the property the same as steps can be converted to slopes. I think its daft to install systems to suit less than 8% of the population especially when the property is not occupied by anyone disabled.